The invention concerns a method of producing a columnar piece whereby a blend of essentially thermoplastic particles is melted into a billet, introduced into a mold, looped into layers inside the mold, and transformed into a piece, subsequent to which the piece is solidified by cooling and removed.
A method of this type is known from German Patent 3 341 438. The thermoplastic material melted in an extruder and transformed into a flexible paste-like strand or "billet" is expanded once it has left the extruder and comes to rest between two open-mesh belts departing from the extruder's outlet. The ratio of the speed at which the billet arrives to that at which the belts travel is adjusted to essentially match the ratio of the distance between the belts to the thickness of the billet. The density of the resulting slab of plastic foam will accordingly essentially equal that of the expanded billet. It is consequently low, and a slab of this type cannot be employed as a static bearing element. The moving belts also make the device needed to carry out the process complicated and sensitive. The products can also essentially only be slabs. The attainable rate of production is, due to the impossibility of diverting heat more rapidly, very low.